Vibration versus Ultrasound analysis (advantage/disadvantage) 1

[alexsurf]

Hello Evrybody,

Could you answer me about this Vibration versus Ultrasound analysis (advantage/disadvantage, reliability) ?

for bearing condition (low and high speed)
for gearmesh condition (low and high speed)

Best regards
Alexsurf

 

[electricpete]

Advantages of vib:
I assume we are talking rolling element bearings. You should be able to get everything you need from vibration including very early warning of bearing defects. In addition vibration can help to assess other machine problems such as unbalance, possibly misalignment, looseness, operation far off B.E.P, cavitation etc. Why does anyone need a redundant tool?

Another thing about vibration is that it has been widely used for a long period of time and the experience base is fairly well developed. From my view ultrasound is a specialized tool used by a few and does not carry that same advantage.

Vibration data collectors are integrated with pc-based vibration software for efficient scheduling, storage, and analysis of data. I dont’ know if ultrasound data can easily be stored or is integrated in the same way.

Possible advantages of ultrasound:
- Might be easier to use to localize some problems (point the probe around and figure out where it’s coming from).
- Might be useful for a cursory inspection of machines that can be seen but are impossible to get to.
- Lots of people use this along with their lub program. If you intend to ignore OEM recommendations for rule-based interval lubrication (using intervals/quantities calculated based on load, speed, bearing size, environment etc), and if you like making simple tasks more complex and time-consuming with unproven improvement in reliability, this may be a good use for you.

Maybe it shows that I have a prejudice towards vib. Others may have different opinions/experiences.

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[McVibe]

I agree with electricpete - If you are interested in condition monitoring of bearings and gearboxes, vibration is the appropriate technology to use (the ultrasound equipment vendors will agree with this statement)

Ultrasound can be useful in lubricating bearings - as electricpete mentioned. You can find an article that talks about this here:

http://www.dliengineering.com/section.asp?nID=16

"Integrating Ultrasound Measurements..."

Obviously, ultrasound is used for a variety of applications that vibration is not used for - such as leak detection...

 

[newtothis]

I have found that ultrasound is better for monitoring very slow rotating (5 RPM) shafts which vibration struggles with. Also if you get a good peice of kit, you can hear the sound the gears or bearing is making and record it.

I also use this as a bck up to FFT, a good bearing sounds like white noise, a good bearing that needs lubrication sounds like very loud white noise and a bearing with wear or damage sounds really rough, find the Alpine components website for examples. Straight vibration is better over 120 RPM but ultrasound is a good back up.